Wheelchair

ABSTRACT

A wheelchair comprises a base frame section with a longitudinal rod carrying at its ends a front wheel and a back wheel, respectively, and a seat frame section for supporting a seat and a back rest. Each back wheel is mounted in a wheel carrier pivotably connected with the corresponding longitudinal rod, wherein a spring is provided between the wheel carrier and the longitudinal rod, the spring extending substantially parallel with the longitudinal rod. Each spring is preferably located below the corresponding longitudinal rod. In this manner the wheelchair described is provided with an elastic back wheel suspension, wherein a compact construction is obtained by the location of the spring.

The invention relates to a wheelchair, comprising a base frame sectionwith a longitudinal rod carrying at its ends a front wheel and a backwheel, respectively, and a seat frame section for supporting a seat anda back rest.

Such a wheelchair is described in U.S. Pat. No. 5,240,277.

The invention aims to provide a wheelchair of this type providing theuser more comfort and which is also suitable for mounting an electricaldrive.

To this end the wheelchair according to the invention is characterizedin that each back wheel is mounted in a wheel carrier pivotablyconnected with the corresponding longitudinal rod, wherein a springmeans is provided between the wheel carrier and the longitudinal rod,said spring means extending substantially parallel with the longitudinalrod.

In this manner a wheelchair is obtained which is provided with anelastic back wheel suspension, wherein a compact construction isobtained by the location of the spring means.

An electrical drive is simply possible if an electric motor is mountedin each wheel carrier, the shaft of said motor carrying the back wheel.

The invention will be further explained by reference to the drawings inwhich an embodiment is very schematically shown.

FIG. 1 is a section of a part of an embodiment of the wheelchairaccording to the invention.

FIG. 2 shows a detail of FIG. 1 at a larger scale.

FIG. 3 is a section according to the plane III--III of FIG. 1.

Referring to the drawings there is schematically shown a wheelchairmainly made in the same manner as the wheelchair according to U.S. Pat.No. 5,240,277 and reference is made to this document for a detaileddescription of the construction of this wheelchair.

The wheelchair comprises a base frame section 1 and a seat frame section2 for supporting a seat not shown and a back rest neither shown, Thebase frame section 1 is provided at both sides with a longitudinal rod 3and 4, respectively, consisting of an oval tube. Each longitudinal rodcarries at its front end a castor wheel 5 and at its rear end a backwheel 6. The back wheel 6 is mounted on the shaft 7 of an electric motor8 not further shown and known per se.

The electric motor 8 is mounted in a wheel carrier 9 pivotably connectedwith the corresponding longitudinal rod 3, 4 by means of a U-shapedbrace 10. To this end the legs of the U-shaped brace 10 are mounted on ashaft 11 rotatably received in a bushing 12 mounted on the longitudinalrod 3, 4 and in the longitudinal rod 3, 4 itself. The U-shaped brace 10is fastened on the shaft 11 by a lock bolt 13 which engages for examplein a circumferential groove of the shaft 11 not shown. Both shafts 11are coupled with each other by a cylindrical bushing 14, the ends of theshafts 11 directed towards each other being fittingly received in saidbushing 14. In this manner the wheel carriers 9 on the one hand canpivot with respect to the base frame section 1 independently of eachother, whereas on the other hand a rigid construction of the base framesection 1 is guaranteed.

Each wheel carrier 9 is coupled with the base frame section 1 by meansof a spring means 15. This spring means 15 is located below thecorresponding longitudinal rod 3, 4 and extends substantially parallelwith this longitudinal rod 3, 4. Thereby a very compact construction isobtained.

As shown in FIG. 2 in more detail, the spring means 15 comprises ahousing 16 and a pulling rod 17, wherein the housing 16 is rotatablyconnected with a support 19 of the corresponding longitudinal rod 3, 4by a pin 18, whereas the pulling rod 17 is rotatably connected with thecorresponding wheel carrier 9. A head 20 of the pulling rod 17 isslidably mounted in the housing 16, wherein a plurality of diaphragmsprings 22 is provided between this head 20 and an end wall 21 of thehousing 16. An adjusting nut 24 is provided on a screw thread part 23 ofthe pulling rod 17, wherein a sleeve 25 is enclosed between theadjusting nut 24 and the end wall 21 of the housing 16. By means of theadjusting nut 24 the rest position of the spring means 15 and therebythe spring bias can be adjusted.

Each wheel carrier 9 is provided with an arm 26 pivotally connected withthe same and carrying a safety wheel 27 at its end directed away fromthe base frame section 1. In the rest position shown in FIG. 1 saidsafety wheel 27 lies at an adjustable distance from the surface 28supporting the wheels 5, 6. The arm 26 is coupled with the base framesection 1 by a coupling rod 29. In the embodiment shown the coupling rod29 is rotatably connected with a support 30 of the arm 26 and a support31 attached to the housing 16. The length of this coupling rod isadjustable for adjusting the distance between the safety wheel 27 andthe surface 28.

If during use of the wheelchair described a back wheel pivots upwardly,the safety wheel 27 will pivot downwardly. Thereby it is obtained thatin particular during riding on an oblique surface tilting backwards ofthe wheelchair is prevented in that the safety wheels 27 will thencontact the oblique surface and thereby increase the wheelbase.

Although in the embodiment described the back wheels 6 are driven byelectric motors 8, it is of course also possible to apply theconstruction described in a wheelchair without electrical drive. In thatcase, each back wheel 6 is connected with an adapted wheel carrier 9 bya shaft.

The invention is not restricted to the above described embodiment whichcan be varied in a number of ways within the scope of the claims.

I claim:
 1. A wheelchair, comprising a base frame section with alongitudinal rod carrying at its ends a front wheel and a back wheel,respectively, and a seat frame section for supporting a seat and a backrest, wherein each back wheel is mounted in a wheel carrier pivotallyconnected to the corresponding longitudinal rod, and a spring meansprovided between the wheel carrier and the longitudinal rod, said springmeans extending substantially parallel with and below the longitudinalrod, wherein each spring means comprises a housing and a pulling rodwith a head slidable in the housing, wherein a plurality of diaphragmsprings are provided between an end wall and the head.
 2. The wheelchairaccording to claim 1, wherein each wheel carrier comprises a U-shapedbrace having legs mounted on a shaft, said shaft being rotatably mountedin the corresponding longitudinal rod.
 3. The wheelchair according toclaim 2, wherein each longitudinal rod includes a bushing for receivingthe corresponding shaft.
 4. The wheelchair according to claim 2, whereinboth shafts are coupled with each other by a cylindrical bushing.
 5. Thewheelchair according to claim 1, and further comprising an arm pivotablyconnected to each wheel carrier and directed away from the base framesection, each arm carrying a safety wheel at its free end, said safetywheel being located at an adjustable distance from a surface supportingthe wheelchair, wherein each arm is connected with the base framesection by a coupling rod.
 6. The wheelchair according to claim 5,wherein the coupling rod has an adjustable length.
 7. The wheel chairaccording to claim 1 wherein the pulling rod has a screw thread partwherein the length projecting out of the housing is adjustable by meansof a nut rotatably mounted on the screw thread part.
 8. The wheelchairaccording to claim 1, and further comprising an electric motor having ashaft mounted in each wheel carrier, the shaft of said motor carryingthe back wheel.
 9. A wheelchair, comprising a base frame section with alongitudinal rod carrying at its ends a front wheel and a back wheel,respectively, and a seat frame section for supporting a seat and a backrest, wherein each back wheel is mounted in a wheel carrier pivotallyconnected to the corresponding longitudinal rod, and a spring meansprovided between the wheel carrier and the longitudinal rod, said springmeans extending substantially parallel with and below the longitudinalrod, wherein each wheel carrier comprises a U-shaped brace having legsmounted on a shaft, said shaft being rotatably mounted in thecorresponding longitudinal rod, both shafts being coupled with eachother by a cylindrical bushing.
 10. The wheelchair according to claim 9,wherein each spring means has an adjustable spring bias.
 11. Thewheelchair according to claim 9, wherein each longitudinal rod includesa bushing for receiving the corresponding shaft.
 12. A wheelchair,comprising a base frame section with a longitudinal rod carrying at itsends a front wheel and a back wheel, respectively, and a seat framesection for supporting a seat and a back rest, wherein each back wheelis mounted in a wheel carrier pivotally connected to the correspondinglongitudinal rod, a spring means provided between the wheel carrier andthe longitudinal rod, said spring means extending substantially parallelwith and below the longitudinal rod, and an arm pivotally connected toeach wheel carrier and directed away from the base frame section, eacharm carrying a safety wheel at its free end, said safety wheel beinglocated at an adjustable distance from a surface supporting thewheelchair, wherein each arm is connected with the base frame section bya coupling rod.
 13. The wheelchair according to claim 12, wherein thecoupling rod has an adjustable length.